JEE Main & Advanced Chemistry Organic Chemistry: Some Basic Principles & Techniques Question Bank Chemical analysis of organic compounds

  • question_answer
    An organic compound gave C = 92.31% and \[H=7.69%\]. If molecular weight of the compound is 78, its molecular formula is

    A) \[{{C}_{6}}{{H}_{6}}\]

    B) \[{{C}_{7}}{{H}_{7}}\]

    C) \[{{C}_{6}}{{H}_{18}}\]

    D) \[{{C}_{8}}{{H}_{20}}\]

    Correct Answer: A

    Solution :

    Element                No. of Moles         Simple Ratio
    C = 92.31 92.31/12 = 7.69 1
    H = 7.69 7.69/1 = 7.69 1
    Hence, CH Empirical formula mass of CH = 13 \[n=\frac{\text{Mol}\text{. mass}}{\text{Emp}\text{.}\,\text{mass}}=\frac{78}{13}=6\] Molecular formula = \[{{(CH)}_{6}}={{C}_{6}}{{H}_{6}}\].


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